Kinases regulate fundamental processes in cancer including tumor proliferation, metastasis, neovascularization, and chemoresistance. Accordingly, kinase inhibitors have been a major focus of drug development and several kinase inhibitors are now approved for various cancer indications. Typically, kinase inhibitors are selected via high throughput screening using catalytic kinase domains at low ATP concentration and this process often yields ATP mimetics that lack specificity and/or function poorly in cells where ATP levels are high.